(a) Field of the Invention
The present invention relates to a catalyst composition and a method of preparing a polyolefin using the same.
(b) Description of the Related Art
A linear alpha-olefin, which is an important material used for a comonomer, a cleaner, a lubricant, a plasticizer, etc., is commercially widely used, and particularly, 1-hexene and 1-octene are commonly used as a comonomer for controlling the density of polyethylene during preparation of linear low-density polyethylene (LLDPE).
In the existing preparation process of LLDPE (Linear Low-Density Polyethylene), copolymerization of ethylene with alpha-olefin, for example, a comonomer such as 1-hexene and 1-octene is carried out in order to control its density by forming branches in a polymer backbone.
Thus, there is a problem in that the cost of comonomers accounts for a large part of the production cost in the preparation of LLDPE having a high content of comonomers. To solve this problem, many different methods have been tried.
Further, since alpha-olefins have a different application field or market size according to the kind, a technology capable of selectively producing specific olefins is commercially very important, and recently, many studies have been carried out on a chromium catalyst technology for preparing 1-hexene or 1-octene with high selectivity through selective ethylene oligomerization.
The existing commercial preparation methods of 1-hexene or 1-octene include a SHOP process of Shell Chemical, a Ziegler process of Chevron Philips, etc., whereby C4˜C20 alpha-olefins of wide distribution may be produced. However, since these methods synthesize alpha-olefins having different lengths at the same time according to a Schulz-Flory distribution, there has been a problem in that it is necessary to perform an additional separation process to obtain a specific alpha-olefin.
To solve this problem, a method of selectively synthesizing 1-hexene through trimerization of ethylene or a method of selectively synthesizing 1-octene through tetramerization of ethylene has been proposed. Further, many studies have been conducted on a catalyst system that enables selective oligomerization of ethylene.
However, although the catalyst system that enables selective oligomerization of ethylene is used, alpha-olefins produced by the oligomerization should be separated and then fed into a copolymerization process as a comonomer, together with ethylene. Thus, there are problems that the process is cumbersome and the production cost is increased.